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NAs produced by integer overflow, but only some time ...

7 messages · William Dunlap, Stefan Th. Gries, Jeff Newmiller +1 more

Stefan Th. Gries
# 
I have problem with integer overflow that I cannot understand.

I have a character vector curr.lemmas with the following properties:

length(curr.lemmas) # 61224
length(unique(curr.lemmas)) # 2652

That vector is the input to the following function:

yules.k1 <- function(input) {
   m1 <- length(input); temp <- table(table(input))
   m2 <- sum("*"(temp, as.numeric(names(temp))^2))
   return(10000*(m2-m1) / (m1*m1))
}

When I run this, I get the following output:

[1] NA
Warning message:
In m1 * m1 : NAs produced by integer overflow

But when I change the function to this one by just replacing m1*m1 by m1^2 ...

yules.k2 <- function(input) {
   m1 <- length(input); temp <- table(table(input))
   m2 <- sum("*"(temp, as.numeric(names(temp))^2))
   return(10000*(m2-m1) / (m1^2))
}

yules.k2(curr.lemmas) # -> 157.261

I am using RStudio 1.1.447 and here's my sessionInfo
######################
R version 3.4.4 (2018-03-15)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Linux Mint 18.3

Matrix products: default
BLAS: /usr/lib/openblas-base/libblas.so.3
LAPACK: /usr/lib/libopenblasp-r0.2.18.so

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
LC_MONETARY=en_US.UTF-8
 [6] LC_MESSAGES=en_US.UTF-8    LC_PAPER=en_US.UTF-8       LC_NAME=C
               LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

loaded via a namespace (and not attached):
 [1] compiler_3.4.4  backports_1.1.2 magrittr_1.5    rprojroot_1.3-2
htmltools_0.3.6 tools_3.4.4     yaml_2.1.19     Rcpp_0.12.16
stringi_1.2.2
[10] rmarkdown_1.9   knitr_1.20      stringr_1.3.0   digest_0.6.15
evaluate_0.10.1
######################

What is even more puzzling is that one time I ran R in the console of
Geany and this happened:
[1] 61224
[1] 3748378176
[1] 3748378176
[1] NA
Warning message:
In m1 * m1 : NAs produced by integer overflow
[1] 3748378176

That is, the multiplication worked with the numbers but not the
numeric vectors; the above is literally copied from the console. Why
is that happening?

Any help would be much appreciated!
STG
--
Stefan Th. Gries
----------------------------------
Univ. of California, Santa Barbara
http://tinyurl.com/stgries
Jeff Newmiller
# 
a) Numeric values may be either integers (signed 32 bit) or double precision (53 bit mantissa).

b) Double precision constants are numeric with no decoration (e.g. 61224). Integer constants have an L (e.g. 61224L).

c) 61224*61224 > 2^31-1 so that answer cannot fit into an integer.

d) Exponentiation is a floating point operation so the result of 61224L^2L is a floating point answer that CAN fit into the 53bit mantissa of a double precision value, so no overflow occurs.

e) Defining a function like yules.k1 and never showing how you called it does not constitute a reproducible example. To avoid such gaffes you can use the reprex package to confirm that the errors shown in your question are in fact reproducible.

f) On this mailing list, the fact that you are using RStudio is at best irrelevant, and at worst off-topic. If you don't see problems running your reproducible example from R in the terminal then the question probably belongs in the RStudio support forum. This is another reason to use the reprex package to check your reproducibility (this works even if you invoke it from RStudio).

g) Calling table on the result of table must be one of the more bizarre calculation sequences I have ever seen in R. I hope you are getting the answers you are expecting when you do use double precision numeric values. Also, using the prefix form of multiplication is unnecessarily obscure, and your use of the return function at the end of your function is redundant.
On May 8, 2018 7:54:26 PM PDT, "Stefan Th. Gries" <stgries at gmail.com> wrote:

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Stefan Th. Gries
    

    

      
      #
    

  


  

      
Before responding to Jeff's posting, let me reiterate my question: Why
does a function using m1*m1 produce an integer overflow, but m1^2 does
not?

As for Jeff's 'response':

            

      
      
      
    

        
Yes, that's all great and I knew that from
<https://stackoverflow.com/questions/8804779/what-is-integer-overflow-in-r-and-how-can-it-happen>.

            

      
      
      
    

        
Responding to a post and never seeing that the provided code does
actually show how I call the function does not constitute a useful
answer. To avoid such gaffes you can use your reading skills to
confirm that the perceived lack of a function call is in fact such a
lack. In addition, typing m1 <- 61224 makes the multiplication example
that I shows in the bottom part of the posting reproducible ...

            

      
      
      
    

        
I did provide the information for the sake of comprehensiveness and I
did mention that the problem also showed up in the console; the whole
second part of the post was on that.

            

      
      
      
    

        
On this mailing list, your assessment of calculation sequences and
their comparison to others you have seen is at best irrelevant and at
worst off-topic since it doesn't answer the question. I didn't ask
(you or anyone) to grade my code and there are reasons why "*" and
return where used there as they are) but to answer the question why
m1*m1 returned an error and m1^2 does not.

  
  


  


      

    

    

      
      

        


  

        

      William Dunlap
    

    

      
      #
    

  


  

      
Printing a number does not show whether it is stored
as a 32-bit integer or as a 64-bit floating point value.
Use. e.g.,  str() or class() to see.
  > str(length(runif(3)))
   int 3
  > str(length(runif(3)) + 1)
   num 4
  > str(length(runif(3)) + 1L)
   int 4
  > str( 3L * 3L )
   int 9
  > str( 3L ^ 2L )
   num 9
You are right that various arithmetic operators map a pair
of integer arguments to various type: the power and division
operators map them to double precision while the the addition,
multiplication, and subtraction operators map them to integer
results (giving NA's if the result cannot fit into 32 bits).
Perhaps it was a mistake to include the integer type, but
at the time S was developed it made sense.

As for table(table(x)) being an unnatural construct, I use it
all the time instead of anyDuplicated to see the pattern of
duplications.


Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Wed, May 9, 2018 at 12:04 AM, Jeff Newmiller <jdnewmil at dcn.davis.ca.us>
wrote:

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

      
      
    

        

  
  


  


      

    

    

      
      

        


  

        

      Stefan Th. Gries
    

    

      
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Ah, ok, _that_ explains it, thanks a lot, I did not know that, which
is why it never occurred to me to check str(m1)!

            

      
      
      
    

        
Thanks for this, too.

  
  


  


      

    

    

      
      

        


  

        

      Jeff Newmiller
    

    

      
      #
    

  


  

      
When you have cooled down you may notice that the answer to your question was in items a-d, though Bill's use of str made it clearer. Also, there was in fact no call to yules.k1, much less one that includes sample data. You will find that the solution to problems in R are very often related to the details of the data you are working with that _you_ aren't noticing, which makes providing sample data a key step to obtaining a straightforward resolution to most problems. There are various discussions online about how to do this. [1][2]

---

[1] http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example

[2] http://adv-r.had.co.nz/Reproducibility.html

        
On May 9, 2018 7:58:19 AM PDT, "Stefan Th. Gries" <stgries at gmail.com> wrote:

            

      
      
      
    

        

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Rolf Turner
    

    

      
      #
    

  


  

      
On 10/05/18 02:58, Stefan Th. Gries wrote:

        

            

      
      
      
    

        
This was made clear in Jeff's initial response.

            

      
      
      
    

        
<SNIP>

Your intemperate reaction to Jeff's response is completely uncalled for. 
  I find Jeff's patience in giving a such a detailed answer to you your 
rather muddled question to be remarkable.

cheers,

Rolf Turner